1. Field of the Invention
The present invention relates to a high-frequency treatment apparatus, used in an irrigation liquid, for performing electric surgery, such as resection, vaporization, or electric coagulation of body tissue.
2. Description of the Related Art
In the past resectoscope apparatuses have been included in high-frequency treatment apparatuses, used in an irrigation liquid, for performing electric surgery, such as resection, vaporization, or electric coagulation of body tissue.
A resectoscope apparatus, generally used for transurethral resection and transcervical resection, primarily includes an elongated hollow sheath to be inserted into the body cavity, a telescope, serving as an endoscope for observation, and an electrode unit for cauterization of body tissue, the telescope and electrode unit being disposed in the sheath.
During observing the body cavity using the resectoscope apparatus, a liquid is supplied through the sheath to the body cavity, thereby providing the field of vision of the endoscope.
In the past, as for the liquid supplied into the body cavity, D-Sorbitol, a nonconductive solution, has been used. A high-frequency current is supplied from an electrode to human body tissue and is then collected by a collector electrode arranged outside of the body.
In the conventional resectoscope apparatus, adductor contraction may be caused by stimulating a nerve through a high-frequency current. Accordingly, nerve block is needed. In addition, D-Sorbitol cannot be supplied into the body cavity for a long time. Unfortunately, time for surgical treatment is limited.
Japanese Unexamined Patent Application Publication No. 2000-201946 discloses a technique to overcome the above-described disadvantages. According to this technique, physiological saline is used as an irrigation liquid that can be supplied into the body cavity of a human being for a long time and a high-frequency current is collected by a sheath instead of a collector electrode, thus reducing nerve stimulation.
FIG. 14 is a diagram showing the structure of a conventional resectoscope apparatus using an irrigation liquid, such as physiological saline.
Referring to FIG. 14, a resectoscope apparatus 901 includes a resectoscope 902, a pack 903 of physiological saline, a liquid supply tube 904, a high-frequency power source 905, an electrode cable 906, and a footswitch 907.
A patient 909 lies on a surgical bed 908.
The distal end 911 of the resectoscope 902 is inserted into the urethra or the like of the patient 909. Referring to FIG. 15, the distal end 911 includes an electrode assembly 914 having an electrode 912 whose distal end part is shaped in a substantially semicircle. The electrode 912 of the electrode assembly 914 is covered with tube members 915 such that only the substantially semicircular distal end part is exposed.
Again referring to FIG. 14, the resectoscope 902 is supplied with physiological saline, serving as an irrigation liquid, from the pack 903 via the liquid supply tube 904. The resectoscope 902 is connected through the electrode cable 906 to the high-frequency power source 905.
When the footswitch 907 is pressed, the high-frequency power source 905 generates a high-frequency current and supplies the current through the electrode cable 906 to the electrode 912 arranged at the tip of the distal end 911 of the resectoscope apparatus 902.
FIG. 16 is a diagram explaining states of the vicinity of the electrode when a high-frequency current is supplied to the electrode 912 at the distal end 911 of the resectoscope 902.
As shown in FIG. 16, after starting of high-frequency current supply to the electrode 912 in an unenergized state, physiological saline is heated in the vicinity of the electrode 912 supplied with thermal energy through the electric impedance of the electrode 912, thus initiating the generation of bubbles 913.
The high-frequency current is further continuously supplied to the electrode 912, thus resulting in an increase of the amount of generated bubbles 913. Thus, the whole periphery of the electrode 912 is covered with the bubbles 913. At that time, the electrode impedance between the electrode 912 and the physiological saline steeply increases, so that a high voltage causes electric discharge. Resection, vaporization, or electric coagulation of body tissue can be achieved by heat generated by the electric discharge.